The invention relates generally to microstructure control in turbine components. In particular, the invention relates to turbine components with different grain sizes and porosities in different regions of the same component.
Different regions of metal alloy gaspath turbine components such as blades and vanes are subjected to widely different thermal mechanical stresses and loading conditions during operation. Airfoils, as an example, are exposed to high temperature centrifugal loading and require high temperature creep resistance. Blade attachments to turbine disks such as fir trees or roots experience lower temperature high contact loading that require high cycle fatigue strength. High temperature creep resistance can be achieved in alloys with large grain sizes. High cycle fatigue strength can be achieved in alloys with fine grain sizes. Successful microstructural design of a single component exposed to these different loading conditions during operation using conventional manufacturing methods normally results in a compromise between at least two microstructures. Areal specific microstructure control in a single monolithic component using conventional manufacturing methods such as casting and forging is difficult.